I think most people have a minisplit as a secondary option. I have a minisplit system. Works fantastic. Works fair down to 17 F. Obviously the efficiency in moving heat from the 17 F outside to the 68 F inside goes down. So, I have a wood stove (and for insurance purposes I have oil-heated hydronic baseboard that is not being used anymore).I didn't realize that. Does the unit just run non-stop then when temps get really cold ?
There are units that work with fair efficiency down to 5 F or so.
THere is a member (@Brian26 I believe) that knows a lot about these.
It would have been cheaper on the coldest days to use the propane, but it wasn't worth the hassle to switch over for me. The coldest day last year for me was Feb. 11th and it got down to -9F overnight, so it was a mild-ish year.